- En masse is defined as something is done collectively, or that it is done all at the same time or all together.
An example of en masse is when a concert ends and the entire audience all tries to exit the stadium at the same time.
People leaving a building en masse.
Origin of en masseFrench literally , in mass
Origin of en masseFrench : en, in + masse, mass.
- in a single body or group; together
- "The net effect of the narrowing passage and the muddy interlude was that the heavy infantry elements arrived to meet the English in disorder (not en masse) - which allows mobbing tactics which ordinarily wouldn't have been available, given their relative numbers." — 
- Alternative spelling of en masse.